 IVES 9 IVES Conference Series 9 Evolution of flavonols during Merlot winemaking processes

Evolution of flavonols during Merlot winemaking processes

Abstract

Aim: The phenomenon of quercetin precipitation in wine (flanovol haze), has been manifested for many years in several wine-producing regions, such as Italy, Australia, and New Zealand (Gambuti et al., 2020; Lanati, Marchi, & Cascio, 2014; Somers & Ziemelis, 1985). Due to the limited information related to the quercetin aglycone behavior and its precursors during wine production in New Zealand, this study aims to monitor the evolution of flavonols and other polyphenols during the commercial fermentation of Merlot grapes, using different fermentation conditions, and vineyard treatments.

Methods: Various trials evaluating sun exposure, winemaking practices, and winemaking process management were undertaken using Merlot grapes, commercial yeast cultures, potassium metabisulphite (20 g/hL), and nutrient supplementation with DYNASTART®-LAFFORT at 20 g/hL. Samples were taken through the winemaking stages, and the polyphenols were quantified using a reversed-phase HPLC method (Garrido-Bañuelos et al., 2019; Peng et al. 2002).

Results: Grapes with elevated amounts of flavonols glycosides produced wines with higher levels of flavonol glycosides and quercetin. Wines made from grapes with greater sun exposure ended up with more flavonol glycosides (89 mg/L) and quercetin (16 mg/L) than the wines elaborated from less exposed grapes (47 mg/L and 9.4 mg/L, respectively). Certain winemaking practices showed differences in quercetin content, for example using small fermentation (250 kg) (12 mg/L), and large fermentation (five tonnes) (28 mg/L). The data also indicates that tannins and total anthocyanins were present at 786 mg/L and 156 mg/L, respectively, for small-scale ferments, and at 888 mg/L and 363 mg/L, respectively, for large-scale ferments. In evaluating the winemaking process management, the ferment pumped over (largest fermentation volume) exhibited flavonol glycosides and quercetin at the highest concentration (91 mg/L and 20 mg/L, respectively), compared to the remaining treatments. PMS, enzyme, and PMS plus enzyme, additions lowered the concentration of the flavonols glycosides at the end of the winemaking process (37 mg/L, 42 mg/L, and 43 mg/L, respectively). It was seem that the PMS plus enzyme (15.6 mg/L) increase quecetin in wine when compared to the control, no additions, (12.6 mg/L). The wines treated with enzyme, PMS, and PMS plus enzyme, also had lower concentrations of anthocyanins (215 mg/L, 233 mg/L, and 238 mg/L, respectively) than the control (291 mg/L).

Conclusions

The study confirmed past research on the role of sun exposure in the formation of flavonols in Merlot grapes and wines. Fermentation size can improve the extraction of polyphenols into wine, and the enzyme additions can promote the hydrolysis of flavonol glycosides. In considering winemaking practices to lower flavonol content, the impact on remaining wine phenolics, of importance to wine colour and mouthfeel, also needs to be carefully evaluated.

DOI:

Publication date: September 14, 2021

Issue: Macrowine 2021

Type: Article

Authors

Cristian Hernandez

School of Chemistry University of Auckland,Paul KILMARTIN, School of Chemistry, University of Auckland Leandro DIAS, School of Food Science, University of Auckland Gianni FLEGO, Villa Maria Estate winery Rebecca DEED, School of Biological Sciences, University of Auckland

Contact the author

Citation

‘Cabernet Sauvignon’ (Vitis vinifera L.) berry skin flavonol and anthocyanin composition is affected by trellis systems and applied water amounts

Trellis systems are selected in wine grape vineyards to mainly maximize vineyard yield and maintain berry quality. This study was conducted in 2020 and 2021 to evaluate six commonly utilized trellis systems including a vertical shoot positioning (VSP), two relaxed VSPs (VSP60 and VSP80), a single high wire (SH), a high quadrilateral (HQ), and a guyot (GY), combined with three levels of irrigation regimes based on different crop evapotranspiration (ETc) replacements, including a 25% ETc, 50% ETc, and 100% ETc. The results indicated SH yielded the most fruits and accumulated the most total soluble solids (TSS) at harvest in 2020, however, it showed the lowest TSS in the second season. In 2020, SH and HQ showed higher concentrations in most of the anthocyanin derivatives compared to the VSPs. Similar comparisons were noticed in 2021 as well. SH and HQ also accumulated more flavonols in both years compared to other trellis systems. Overall, this study provides information on the efficacy of trellis systems on grapevine yield and berry flavonoid accumulation in a currently warming climate.

Anthocyanin profile is differentially affected by high temperature, elevated CO₂ and water deficit in Tempranillo (Vitis vinifera L.) clones

Anthocyanin potential of grape berries is an important quality factor in wine production. Anthocyanin concentration and profile differ among varieties but it also depends on the environmental conditions, which are expected to be greatly modified by climate change in the future. These modifications may significantly modify the biochemical composition of berries at harvest, and thus wine typicity. Among the diverse approaches proposed to reduce the potential negative effects that climate change may have on grape quality, genetic diversity among clones can represent a source of potential candidates to select better adapted plant material for future climatic conditions. The effects of individual and combined factors associated to climate change (increase of temperature, rise of air CO2 concentration and water deficit) on the anthocyanin profile of different clones of Tempranillo that differ in the length of their reproductive cycle were studied. The aim was to highlight those clones more adapted to maintain specific Tempranillo typicity in the future. Fruit-bearing cuttings were grown in controlled conditions under two temperatures (ambient temperature versus ambient temperature + 4ºC), two CO2 levels (400 ppm versus 700 ppm) and two water regimes (well-watered versus water deficit), both in combination or independently, in order to simulate future climate change scenarios. Elevated temperature increased anthocyanin acylation, whereas elevated CO2 and water deficit favoured the accumulation of malvidin derivatives, as well as the acylation and tri-hydroxylation level of anthocyanins. Although the changes in anthocyanin profile observed followed a common pattern among clones, such impact of environmental conditions was especially noticeable in one of the most widely distributed Tempranillo clones, the accession RJ43.

Investigating the impact of grape exposure and UV radiations on rotundone in Vitis vinifera L. Tardif grapes under field trial conditions

Rotundone is the main aroma compound responsible for peppery notes in wines whose biosynthesis is negatively affected by heat and drought. Through the alteration of precipitation regime and the increase in temperature during maturation, climate change is expected to affect wine peppery typicality. In this context there is a demand for developing sustainable viticultural strategies to enhance rotundone accumulation or limit its degradation. It was recently proposed that ultraviolet (UV) radiations could stimulate rotundone production. The aim of this study was to investigate under field trial conditions the impact of grape exposure and UV treatments on rotundone in Vitis vinifera L. Tardif, an almost extinct grape variety from south-west France that can express particularly high rotundone levels. Four different treatments were compared in 2021 to a control treatment using a randomised complete block design with three replications per treatment. Grape exposure was manipulated through early or late defoliation. Leaf and laterals shoots were removed at Eichorn Lorenz growth stages 32 or 34 on the morning-sun side of the canopy. During grape maturation, UV radiations were either reduced by 99% by installing UV radiation-shielding sheets, or applied four times using the Boxilumix™ non thermal device (Asclepios Tech, Tournefeuille) with the aim of activating plant signalling pathway. Loggers displayed in solar radiation shields were used to assess the effect of such shielding sheets on air temperature within the bunch zone. The composition of grapes subjected to these treatments will be soon analysed for their rotundone content and basic classical laboratory analyses. Grapes will be harvested to elaborate wines under standardized small-scale vinification conditions (60kg) that will be assessed by a trained sensory panel.

Grapevine varietal diversity as mitigation tool for climate change: Agronomic and oenologic potential of 14 foreign varieties grown in Languedoc region (France)

Climate change effects in Languedoc include an expected rise in temperatures, increased evapotranspiration as well as more severe and frequent climatic hazards, such as frost, drought periods and heat waves. For winegrowers theses phenomena impact both yield and quality, resulting in more frequent unbalanced wines. Research on identified mitigation tools for vineyard management is necessary to improve resilience of grapevine agrosystems. Varietal assortment is one of them. This study focuses on agronomic and oenologic potential of 14 foreign varieties grown in Languedoc French region. Fourteen grapevine varieties were monitored during 2021 from June until harvest on eight different sites, some of which occurring on more than one site adding up to 21 different modalities: 7 white varieties Alvarinho B, Assyrtiko B (2), Malvasia Istriana B, Parellada B, Verdejo B, Verdelho B, Xarello B, and 7 black varieties Saperavi N (2), Touriga nacional N, Baga N, Aleatico N, Montepulciano N (2), Primitivo N (3), Calabrese N (3). Varietals were compared through the following parameters: phenology was assessed by using the information collected in the Database Network of French Vine Conservatories (INRAE-SupAgro-IFV, 2005-2015). The number of inflorescences for shoots from secondary buds and bourillons and suckers were observed to assess post-bud break frost tolerance potential. Grapevine water status was studied through stem water potential measurement, observation of foliage symptoms of drought, and 𝛿13C on must. Frequencies and intensities of downy mildew, powdery mildew, and black rot attacks were estimated before harvest on leaves and clusters and botrytis at harvest to assess disease susceptibilities. Berry composition was monitored from end of veraison until harvest. Yield and mean bunch weight were also calculated. Varieties were then ranked on a 1-4 scale for each parameter and compared through PCA. Forty two stations of the Mediterranean basin were compared by PCA with the Multicriteria Climatic Classification indicators in order to confront the collected information during 2021 campaign to the hypothesis that plants coming from dry and hot regions are genetically adapted to such climatic conditions.

Geospatial trends of bioclimatic indexes in the topographically complex region of Barolo DOCG

Barolo DOCG is an economically important wine producing region in Northwest Italy. It is a small region of approximately 70 km2 gross area. The topography is very complex with steep sloped hills ranging in elevation from below 200 m to 550 m. Barolo DOCG wine is made exclusively from the Nebbiolo grape. Bioclimatic indexes are often used in viticulture to gain a better understanding of broader climate trends which can be compared temporally and geographically. These indexes are also used for identifying potential phenological timing, growing region suitability, and potential risks associated with expected climatic changes. Understanding how topography influences bioclimatic indexes can help with understanding of mesoscale climate behaviour leading to improved decision making and risk management strategies. The average monthly maximum and minimum temperatures, the Cool Night Index, the Huglin Index, and the monthly diurnal range (from July to October) were calculated using data from 45 weather stations within a 40 km radius of the Barolo DOCG growing area between the years 1996 and 2019. Linear and multiple regression models were developed using independent variables (elevation, aspect, slope) extracted from a digital elevation model to identify significant relationships. Bioclimatic indexes were then kriged with external drift using independent variables that showed significant relationships with the bioclimatic index using a 100 m resolution grid. The maximum monthly temperatures and the Huglin Index showed consistent significant negative relationships with elevation in all years. The minimum monthly temperatures showed no relationship with elevation but in some months a small but significant relationship was observed with aspect. Due to the lack of a relationship between minimum monthly temperatures and elevation compared to the significant relationship between maximum monthly temperatures and elevation, monthly diurnal range had a negative relationship with elevation.